(a) Technical Field
The present disclosure relates to an apparatus for preventing overcharging of a battery and a battery comprising the apparatus that disconnects a charging circuit by sensing the swelling even in a minimal amount of gas generation.
(b) Background Art
Generally, an overcharging safety device is mounted within a high voltage battery system. The overcharging safety device is designed to prevent an outbreak of fire by cutting off the flow of electric current and hindering thermal runaway therethrough when an overcharge occurs in the battery system. The mechanism of an overcharging safety structure of a conventional passive type uses expansion force generated during swelling of a cell. When the swelling of the cell is sufficiently generated, a cell tap is ruptured through a cell expansion induced by an opening of an end plate, thereby cutting off electric current to ensure safety of the high voltage battery system.
However, in this structure, the swelling of the cell has to be sufficiently generated before an occurrence of thermal runaway, and when the swelling of the cell is insufficiently generated before the occurrence of thermal runaway, the swelling of the cell will occur simultaneously with the thermal runaway, and thus, even when an electrical current is cut off, a fire may outbreak due to the thermal runaway. Additionally, when the amount of gas generation is not sufficiently maintained when the specification of a cell is changed, a design change of the battery system is required due to the variation of cell expansion force. That is, it may be difficult to dynamically ensure a safety structure which is sensitive to the specification of a cell. Further, even for a safety structure of an active type, which blocks a relay actively, an overcharging safety structure of a passive type is required since it may be difficult to ensure safety when the relay is fused to fail.
The technology according to an exemplary embodiment of the present invention relates to an overcharging safety structure of a passive type, and it uses a minimal amount of gas generation. In other words, the technology relates to an overcharging safety structure for cutting off an electrical current in an early stage through the cell expansion force with a minimal amount of gas generation. The overcharging safety structure of a conventional passive type uses an expansion force in a direction of a battery surface which is generated when a cell swells. When the swelling of the cell swelling is sufficiently generated, a cell is deformed at an endplate opening and a welding point of a cell tap portion and a bus bar is ruptured through the deformation of the cell, thereby ensuring safety by cutting off an electrical current through the rupture of welding point/cell tap portion.
However, the swelling of the cell has to be sufficiently generated before an occurrence of thermal runaway under this structure since when the swelling of the cell is insufficiently generated in a direction of a battery surface before an occurrence of the thermal runway, the swelling of the cell may occur simultaneously with the thermal runaway. Thus, even when an electrical current is cut off, a fire may outbreak due to the thermal runaway. Additionally, when the specification of a cell is changed, a design change of the battery system is required due to the variation of cell expansion force.
A sensor or switch configured to sense the cell expansion is arranged on the safety structure of a conventional active type and the power of a relay is to be cut off when the cell expansion is sensed, thus cutting off current flow of a battery system. However, a technology for cutting off the power of a relay cannot be applied to the case where the relay is fused to fail. Accordingly, it may be difficult to ensure safety when an emergency situation such as an accident, beyond operation of a sensor or switch, failure of electron components or the like occurs simultaneously together with the swell expansion according to an overcharging safety structure of an active type.
Further, according to a related art a space for allowing the surface expansion of a cell has to be prepared and thus a space for a package is increased, causing unfavorable an energy density per volume. The description provided above as a related art of the present invention is merely for helping understanding the background of the present invention and should not be construed as being included in the related art known by those skilled in the art.